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Can't get power to A/C clutch
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Watercooled
Novice
Jan 19, 2016, 5:59 PM
Post #1 of 17
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Can't get power to A/C clutch
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2001 Dodge Cargo Van 2500
318 V-8
165,000 miles
The A/C was fine yesterday. Today the clutch will not engage. There is no power going to the wire that operates the clutch. The 20 A fuse is good and power is going through it. The evaporator fan and the other controls work normally. The clutch engages when power is applied directly to it, so I say it is good. There is 80 pounds of pressure in the system. I checked the low pressure and high pressure switches. They both show continuity. I shorted around both switches and still no power, no clutch.
My mechanic checked with the computer. He said it recognized the call for cool, but did not see the delivery of power to the clutch. I believe he said there is a relay and the relay is functioning. We will try again in the morning. I am doing some homework tonight.
I have traced as much wire as I can trace. The wire carrying power from the fuse block is red with a yellow stripe. I have no idea where it goes. It is not present at the A/C switches in the console. If there are any other controls that would prevent power from reaching the clutch, I am not aware of them. I see no burning, shorting, cutting, abrading, or trauma to any wires anywhere under the dash or in the engine compartment.
Is there a diagram? Is the relay bad? Is there even a relay?
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Discretesignals
Ultimate Carjunky
/ Moderator
Jan 19, 2016, 6:47 PM
Post #2 of 17
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Re: Can't get power to A/C clutch
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Tell your mechanic to do an ATM test with his/her scan tool. He/she should know this if they work on vehicles for a living. If he/she has a scan tool that can perform that function, he/she can find out which side of the system to focus on. The ATM test will activate relays on and off regardless of the input logic to the PCM from the switches and request. The AC clutch relay is in the power distribution center under the hood.
Curious, but why are you finding out answers for your mechanic?
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Jan 19, 2016, 7:18 PM)
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Discretesignals
Ultimate Carjunky
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Jan 19, 2016, 7:11 PM
Post #3 of 17
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Re: Can't get power to A/C clutch
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Those diagrams don't match what I have.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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Hammer Time
Ultimate Carjunky
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Jan 19, 2016, 7:59 PM
Post #4 of 17
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Re: Can't get power to A/C clutch
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That's an '01 2500 Van with a 5.2. straight from Alldata
2001 Dodge or Ram Truck RAM 2500 Truck 2WD V8-5.2L VIN Y
Vehicle » Heating and Air Conditioning » Diagrams » Electrical Diagrams
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
(This post was edited by Hammer Time on Jan 19, 2016, 7:59 PM)
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Watercooled
Novice
Jan 19, 2016, 9:52 PM
Post #6 of 17
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Re: Can't get power to A/C clutch
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I am finding our for myself. I checked out what I could before I took the VAN to him. It was late, he was pressed, I suggested we try it again in the morning.
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Watercooled
Novice
Jan 19, 2016, 10:18 PM
Post #7 of 17
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Re: Can't get power to A/C clutch
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Well, now I have a diagram. Still figuring out how to read it. I guess the numbers are printed on the actual wires? I will pass on tracing invisible wires
The red wire with the yellow stripe comes from the fuse in the fuse block.
I don't see on the diagram where there is a fuse for the A/C circuit. But I do see several fuses inline in the A/C circuit. My van has a 20 A fuse labeled "A/C Clutch". The red wire with the yellow stripe comes from the fuse and goes into a bundle that goes into a void under the dash.
We will see what the ATM reveals.
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Discretesignals
Ultimate Carjunky
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Jan 19, 2016, 10:57 PM
Post #8 of 17
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Re: Can't get power to A/C clutch
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Chrysler's ATM test is a great tool because you can eliminate the PCM's output driver, wiring to the relay, the relay itself, the wiring from the relay to the clutch, and the powers and grounds that are used by the relay and the clutch coil without even breaking out a volt meter. If you can actuate the clutch doing an ATM test with the scan tool, then focus on the input side of the PCM. The input side includes the switches and controls, but it also includes the PCM's internal logic which is not shown in the wiring schematic.
It is important to think about what the PCM needs in order to activate the clutch relay. One thing that you cannot really get from a wiring schematic is what type of logic the PCM uses to decide to turn the ac on. You do know the PCM needs to see a certain voltage from the switches, but there are other logical inputs that are not shown; i.e: engine rpm, tps voltage, ect voltage, system voltage, ect. Most of the time knowledge of the internal logic comes from reading the theory and operation of the system or experience. Got plenty of both..lol.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Jan 19, 2016, 11:05 PM)
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Hammer Time
Ultimate Carjunky
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Jan 20, 2016, 3:23 AM
Post #9 of 17
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Re: Can't get power to A/C clutch
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Looks like you were right........... (as usual)
Lets try this again
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Watercooled
Novice
Jan 20, 2016, 7:41 AM
Post #10 of 17
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Re: Can't get power to A/C clutch
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OK. I am in a better position now. Yes it’s true – You can buy a scan tool but you can’t buy experience. This will be solved this morning at the mechanic’s, I’m sure. We will see how well he knows his tool. This all started after he used the scan tool to find the cause of a misfire, which was one injector not getting power. A critter had chewed the wire in two! After that I had warning lights that weren't there before. He said the code needed to be reset, but the computer wasn't letting him in. Then it was late and he was pressed and I left. After chatting with you guys, I am convinced the PCM needs to get right before my A/C will work. Maybe a re-boot? The rest of the system is probably fine.
If you are still interested I would like to figure some things out. I think I can read this diagram, but I don’t recognize some of these symbols and some of the terminology. Is there a legend that identifies these symbols? I also don’t know which direction the DC current travels. Positive to Negative, or vice versa?
In the A/C clutch relay I see a coil, and a rectangle with a slash through it. Must be a solenoid. Then in the A/C clutch itself, where a coil would be, I see the arrows. Then the rectangle again. What are the arrows?
Then above the clutch relay, there is a dotted line connecting the RD/YL wire to the RD/DG wire. Does the dashed line indicate that they both use the same plastic connector?
Then above that, in Joint Connector #3 there is the horizontal line with an arrow point. That symbol is in other places also.
What is a Joint Connector? What do you call those plastic things that - for example - connect the two wires at the compressor? What are those "Y" and "Inverted Y" symbols at the end of the wires?
I appreciate the valuable input.
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Hammer Time
Ultimate Carjunky
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Jan 20, 2016, 10:59 AM
Post #11 of 17
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Re: Can't get power to A/C clutch
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
(This post was edited by Hammer Time on Jan 20, 2016, 12:17 PM)
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kev2
Veteran
Jan 20, 2016, 12:55 PM
Post #12 of 17
(1508 views)
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Re: Can't get power to A/C clutch
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Why not share ALL the codes and issues - before reflashing / rebooting and blaming the PCM...
A somewhat simple circuit to need 11 post, multiple wiring diagrams and suggestions.
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Tom Greenleaf
Ultimate Carjunky
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Jan 20, 2016, 1:08 PM
Post #13 of 17
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Re: Can't get power to A/C clutch
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Quote on post #10 ">>A critter had chewed the wire in two!<<"
Aren't then special? Just a comment on damage like that by critters. You may not know if there's lots more messing you all up so look. Anything possible and a good reason for no power to A/C clutch. Pretty sure the Mopars will default to shut down clutch with assorted problems for real and bad info on the list. What that might have done to ECM unknown but doesn't sound so great to me.
So. In times when damage like that found I find they like hood insulation and somehow wires are tasty but not so much hard plastic encased things like a relay or other items. It will happen again just as fast if not tended to.
Gotta get thru this and stop it so some suggestions.
Virtually ALL vehicles that had this problem were parked in the same spot even daily or stored - some horror shows.
What can help. Park backed in or forward from what you were doing! Dryer softener sheets help. Mothballs no longer made of same product but would try some hanging in harmless places anyway.
IDK your situation but I use rat poison in bags as two stored vehicles are always out of pets or children's reach said not to kill non rodents rather make then throw up - rodents can't throw up - no kidding, so it harms them and may not kill them but they go away.
Ages ago did a thread on this and found those silent noise things were not conclusive and annoyed other things?
You'll never win at assorted problems if not rid of the critters. Call for an exterminator if needed.
They have to go,
T
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Watercooled
Novice
Jan 21, 2016, 7:59 AM
Post #14 of 17
(1487 views)
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Re: Can't get power to A/C clutch
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Ok, Hammer Time -- Those two pages are a major help. Along with some other sites I am beginning to see a bigger picture.
My mechanic is turning this case over to his boss, who is not available until tomorrow, Friday 22nd. I just have to wait and see if Big Boss can start at the top and work his way through. In the meantime I will continue to study this. It's fascinating. If you take the PCM out of the equation, it becomes a simple circuit. If I just had that little gadget that allows you to read the pins on the clutch relay ...
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Hammer Time
Ultimate Carjunky
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Jan 21, 2016, 8:05 AM
Post #16 of 17
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Re: Can't get power to A/C clutch
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The PCM always has to control the relay because it monitors other inputs before it makes a decision to turn the relay on.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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kev2
Veteran
Jan 21, 2016, 8:22 AM
Post #17 of 17
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Re: Can't get power to A/C clutch
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Codes- a malfunction in a system MAY cause the PCM (logic) to restrict AC.... ie a code for temp sensor.
Relay - why not swap with another relay of same type - often we will swap in something like "horn" just for testing.
Relays sometimes will have the cavity numbers printed on them- 30, 85, 86, 87, 87a- OR google "automotive relay pin out"
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